2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)-phenyl]-2H-benzotriazole and stabilized compositions

ABSTRACT

2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole exhibits outstanding efficacy in protecting organic substrates from light induced deterioration as well as good resistance to loss by volatilization or exudation during the high temperature processing of stabilized compositions. The combination of the benzotriazole UV absorber with a hindered amine light stabilizer is particularly efficacious in protecting thermoset and thermoplastic acrylic resin automotive finishes and enamels.

This is a divisional of application Ser. No. 36,914, filed May 10, 1979, issue fee paid, which in turn is a Continuation-in-part of application Ser. No. 918,984, filed June 26, 1978, now U.S. Pat. No. 4,226,763, issued Oct. 7, 1980.

BACKGROUND OF THE INVENTION

The present invention relates to selected 2-aryl-2H-benzotriazoles which are useful in protecting light-sensitive organic materials from deterioration and to stabilized compositions containing said benzotriazoles.

The UV-absorber of the o-hydroxyphenyl-2H-benzotriazole class have long been known as effective light stabilizers for organic materials and have enjoyed considerable commercial success.

The description, preparation and uses of these valuable 2-aryl-2H-benzotriazoles are further taught in U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615 and 3,230,194.

However the hitherto known 2-aryl-2H-benzotriazoles of this group have in some circumstances exhibited limited compatibility in certain substrates, and excessive tendency to exude, sublime and/or volatilize during processing of stabilized compositions into sheets, films, fibers or other pellicles when processing must be done at elevated temperatures. Likewise such benzotriazoles may also suffer undue loss by volatilization or sublimation from fabricated structures, particularly thin films or coatings, especially when subjected to elevated temperatures during use.

Attempts have been made to increase compatibility and to reduce volatilization loss by modifying the structure of the benzotriazoles.

In U.S. Pat. No. 3,230,194, a higher alkyl group was substituted for methyl and the compound 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole exhibited superior compatibility and performance in polyethylene.

In U.S. Pat. No. 4,127,586 still other modifications to the 2-aryl-2H-benzotriazole moiety were made to increase still further compatibility in substrates and resistance to volatilization. The compound 2-[2-hydroxy-3-(1-phenylethyl)-5-methylphenyl]-2H-benzotriazole described therein exhibited better compatibility and better resistance to loss by volatilization during processing than did the earlier prior art benzotriazole compounds.

In Japanese Kokai No. 158588/75, other benzotriazole light stabilizers such as 2-(2-hydroxy-3-α,α-dimethylbenzyl-5-methylphenyl)-2H-benzotriazole are disclosed.

However, still better resistance to loss from stabilized compositions during high temperature processing remained a practical objective and need in the art for the benzotriazole UV-absorbers.

The instant compounds such as 2-[2-hydroxy-3,5-di(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole exhibit surprisingly superior resistance to loss from stabilized compositions during high temperature processing or in end use applications where coatings or films of the stabilized compositions are exposed even to ambient weathering and light exposures compared to stabilized compositions containing the 2-aryl-2H-benzotriazoles of the prior art.

In U.S. Pat. No. 4,041,044 an improved process for making 2-aryl-2H-benzotriazoles is taught. In the broadest generic scope in said reference, 2-[2-hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole and 5-chloro-2-[2-hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole are disclosed. Neither compound was exemplified nor prepared in said reference and the outstanding properties of these compounds now seen compared to other prior art benzotriazoles were not then recognized from the myriad of possible compounds generically disclosed in this reference.

In copending U.S. Application Ser. No. 971,271 the use of hindered amine light stabilizers to protect metallic lacquers is described.

In copending U.S. Application Ser. No. 6391 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2-H-benzotriazole is described.

DETAILED DISCLOSURE

This invention pertains to selected 2-aryl-2H-benzotriazole light absorbers and to organic materials, boty polymeric and non-polymeric, stabilized thereby.

More particularly, the 2-aryl-2H-benzotriazoles of this invention are represented by the Formula A ##STR1## wherein T₁ is hydrogen or chloro,

T₂ and T₃ are independently the group ##STR2## where T₄ is hydrogen or lower alkyl.

When T₄ is lower alkyl, the alkyl group is in the meta or para position, usually the para position. Typical lower alkyl groups are methyl, ethyl, isopropyl, tert-butyl, tert-amyl and sec-hexyl.

Preferably the instant compounds are those where T₂ and T₃ are the same and T₄ is hydrogen or p-methyl.

Most preferably T₄ is hydrogen.

Particularly preferred is the compound 2-[2-hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole.

The instant invention embraces the 2-aryl 2H-benzotriazoles of formula B ##STR3## wherein T₁ is hydrogen or chloro,

T₅ is tert-octyl or the group ##STR4## where T₄ is hydrogen or lower alkyl,

T₆ has the same meaning as T₅, with the proviso that one of T₅ and T₆ must be tert-octyl, but both cannot be tert-octyl.

Preferably T₄ is hydrogen or p-methyl and most preferably is hydrogen.

Particularly preferred are the compounds 2-[2-hydroxy-3-tert-octyl-5-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole and 2-[2-hydroxy-3-(α,α-dimethylbenzyl)-5-tert-octylphenyl]-2H-benzotriazole.

SYNTHESIS OF COMPOUNDS

The compounds of this invention are made by the following procedure: ##STR5## X is an anion such as chloride or sulfate. ##STR6##

T₁, T₂ and T₃ are as described earlier in the specification.

The benzotriazoles of Formula Ia are also made of the same general procedure.

Step I is the coupling of a diazonium compound with a phenol and can be carried out under either acid or alkaline conditions. When the coupling of the phenols bearing an aralkyl group in one ortho position to the hydroxyl moiety is carried out in acid medium, the yields of coupled product, the o-nitroazobenzene intermediate (F), are generally under 50% of theory.

Surprisingly when the same coupling reaction is carried out in strongly alkaline medium (pH over 10), the diazonium solution couples with facility to the phenol giving high yields (over 80% of theory) of the intermediate (F).

Step II involves the reductive cyclization of the intermediate F to the corresponding 2-aryl-2H-benzotriazole. This can be conveniently carried out by a number of known reduction methods including zinc and alkali, hydrazine, and catalytic hydrogenation with noble metal or nickel catalysts for this reaction. Good yields of the 2-aryl-2H-benzotriazoles are obtained by using such systems.

The various starting materials, i.e., phenols, o-nitroaniline, 5-chloro-2-nitroaniline, α-methylstyrene, are largely available as items of commerce or can easily be prepared by known methods.

The compounds of this invention are effective light stabilizers in a wide range of organic polymers. Polymers which can be stabilized include:

1. Polymers which are derived from mono- or diolefins, e.g., polyethylene which can optionally be crosslinked, polypropylene, polyisobutylene, polymethylbutene-1, polymethylpentene-1, polyisoprene, polybutadiene.

2. Mixtures of the homopolymers cited under (1), for example mixtures of polypropylene and polyethylene, polypropylene and polybutene-1, polypropylene and polyisobutylene.

3. Copolymers of the monomers based on the homopolymers cited under (1), for example ethylene/propylene copolymers, propylene/butene-1 copolymers, propylene/isobutylene copolymers, ethylene/butene-1 copolymers as well as terpolymers of ethylene and propylene with a diene, for example hexadiene, dicyclopentadiene or ethylidene norbornene, and copolymers of α-olefins, e.g., ethylene with acrylic or methacrylic acid.

4. Polystyrene.

5. Copolymers of styrene and of α-methylstyrene, for example styrene/butadiene copolymers, styrene/acrylonitrile copolymers, styrene/acrylonitrile/methacrylate copolymers, styrene/acrylonitrile copolymers modified with acrylic ester polymers to provide impact strength as well as block copolymers, e.g., styrene/butadiene/styrene block copolymers.

6. Graft copolymers of styrene, for example the graft polymer of styrene to polybutadiene, the graft polymer of styrene with acrylonitrile to polybutadiene as well as mixtures thereof with the copolymers cited under (5), commonly referred to as acrylonitrile/butadiene/styrene or ABS plastics.

7. Halogen-containing vinyl polymers, for example polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polychloroprene, chlorinated rubbers, vinyl chloride/vinylidene chloride copolymers, vinyl chloride/vinyl acetate copolymers, vinylidene chloride/vinyl acetate copolymers.

8. Polymers which are derived from α,β-unsaturated acids and derivatives thereof, polyacrylates and polymethacrylates, polyacrylic amides and polyacrylonitrile. The instant compounds are advantageously used in heat-curable acrylic resin lacquers which are composed of a copolymer of acrylic acid and one or more of its derivatives, and a melamine-formaldehyde resin.

9. Polymers which are derived from unsaturated alcohols and amines and from the acyl derivatives thereof or acetals, for example polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl maleate, polyvinyl butyral, polyallyl phthalate, polyallyl melamine and copolymers thereof with other vinyl compounds, for example ethylene/vinyl acetate copolymers.

10. Homopolymers and copolymers which are derived from epoxides, for example polyethylene oxide or the polymers which are derived from bis-glycidyl ethers.

11. Polyacetals, for example polyoxymethylene, as well as polyoxymethylenes which contain ethylene oxide as comonomer.

12. Polyalkylene oxides, for example polyoxyethylene, polypropylene oxide or polyisobutylene oxide.

13. Polyphenylene oxides.

14. Polyurethanes and polyureas, such as in urethane coatings.

15. Polycarbonates.

16. Polysulfones.

17. Polyamides and copolyamides which are derived from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams, for example polyamide 6, polyamide 6/6, polyamide 6/10, polyamide 11, polyamide 12, poly-m-phenylene-isophthalamide.

18. Polyesters which are derived from dicarboxylic acids and dialcohols and/or from hydroxycarboxylic acids or the corresponding lactones, for example polyethylene glycol terephthalate, poly-1,4-dimethylol-cyclohexane terphthalate.

19. Cross-linked polymers which are derived from aldehydes on the one hand and from phenols, ureas and melamine on the other, for example phenol/formaldehyde, urea/formaldehyde and melamine/formaldehyde resins.

20. Alkyd resins, for example glycerol/phthalic acid resins and mixtures thereof with melamine/formaldehyde resins.

21. Unsaturated polyesters resins which are derived from copolyesters of saturated and unsaturated dicarboxylic acids with polyhydric alcohols as well as from vinyl compounds as cross-linking agents and also the halogen-containing, flame-resistant modifications thereof.

22. Natural polymers, for example cellulose, rubber, as well as the chemically modified homologous derivatives thereof, for example cellulose acetates, cellulose propionates and cellulose butyrates and the cellulose ethers, for example methyl cellulose.

While compounds of this invention are very effective stabilizers for a host of organic substrates subject to light induced deterioration, as are the 2-aryl-2H-benzotriazole light absorbers in general, the instant compounds with their surprising resistance to loss from a stabilized composition during high temperature processing due to volatilization, exudation or sublimation have particular value in stabilizing polymeric substrates which are perforce processed at elevated temperatures.

Thus, the compounds of this invention are particularly useful as stabilizers for the protection of polyesters, for instance poly(ethylene terephthalate), poly(butylene terephthalate) or copolymers thereof; of polycarbonates, for example polycarbonate derived from bisphenol A and phosgene, or copolymers thereof; of polysulfones; of polyamides such as nylon-6, nylon-6,6, nylon 6,10 and the like as well as copolyamides; of thermoset acrylic resins; of thermopolastic acrylic resins; of polyolefins such as polyethylene, polypropylene, copolyolefins and the like; and of any polymer system requiring high temperature processing and fabrication.

Certain hydrophobic nondiffusing hydroxyphenylbenzotriazoles are disclosed as very useful as ultraviolet light absorbers in photographic gelatin layers (U.S. Pat. No. 3,253,921). The instant benzotriazoles with their great resistance to volatilization, their desirable absorption characteristics in the ultraviolet range and their photographic inertness are particularly useful in photographic compositions, especially in protecting color dye images against the harmful effects of ultraviolet light.

Of particular interest are the thermoplastic acrylic resins and the thermoset acrylic resins used in automotive finishes and enamels. These materials are described in the Encyclopedia of Polymer Science and Technology, Interscience Publishers, New York, Vol 1 (1964), pages 273-276, and Vol 13 (1970), pages 530-532; and W. R. Fuller, "Understanding Paint," American Paint Journal Co., St. Louis, 1965, pages 124-135.

The acrylic resin lacquers which according to the invention can be stabilised against light, moisture and oxygen are the customary acrylic resin stoving lacquers, such as are described for example in H. Kittel's `Lehrbuch der Lacke und Beschichtungen` (Textbook of Lacquers and Coatings), Volume 1, part 2 on pages 735 and 742 (Berlin, 1972), and in H. Wagner, H. F. Sarx, `Lackkunstharze` (Synthetic resins for Lacquers), on pages 229-235.

Of particular interest is the stabilisation, according to the invention, of metallic lacquers based on hot-crosslinkable polyacrylate resins which contain styrene incorporated by polymerisation. It would be possible with these resins to produce metallic lacquers having excellent physical and chemical properties if it were not for the formation of cracking on weathering, depending of the content of incorporated styrene. Other lacquers and enamels are those based on alkyl-melamine and alkyd-acrylic malamine resins.

For obtaining the metallic effect, there are used the aluminium pigments normally employed for this purpose in an amount of 1 to 10 percent by weight, relative to the solvent-free binder (lacquer resin). The application of the metallic lacquers stabilised according to the invention is effected preferably, in the usual manner, by one of two processes; either by the single-layer process or by the two-layer process. In the latter case, the layer containing the aluminium pigment is firstly applied, and then over this is applied a covering clear-lacquer layer.

Although the compounds of the invention may be used above to provide a light stabilizing function, the compounds of this invention are often combined with other stabilizers, even other light stabilizers, in the preparation of stabilized compositions. The stabilizers may be used with phenolic antioxidants, pigments, colorants or dyes, light stabilizers such as hindered amines, metal deactivators, etc.

In general, the stabilizers of this invention are employed from about 0.1 to about 5% by weight of the stabilized composition, although this will vary with the particular substrate and application. An advantageous range is from about 0.5 to about 3%.

The stabilizers of Formula I may readily be incorporated into the organic polymers by conventional techniques, at any convenient stage prior to the manufacture of shaped articles therefrom. For example, the stabilizer may be mixed with the polymer in dry powder form, or a suspension or emulsion of the stabilizer may be mixed with a solution, suspension, or emulsion of the polymer. The stabilized polymer compositions of the invention may optionally also contain from about 0.1 to about 5%, preferably from about 0.5 to about 3% by weight of various conventional additives, such as the following, particularly phenolic antioxidants or light-stabilizers, or mixtures thereof:

1. ANTIOXIDANTS

1.1 Simple 2,6-dialkylphenols, such as, for example, 2,6-di-tert.-butyl-4-methylphenol, 2-tert.-butyl-4,6-dimethylphenol, 2,6-di-tert.-butyl-4-methoxymethylphenol and 2,6-dioctadecyl-4-methylphenol.

1.2 Derivatives of alkylated hydroquinones, such as for example, 2,5-di-tert.-butyl-hydroquinone, 2,5-di-tert.-amylhydroquinone, 2,6-di-tert.-butyl hydroquinone, 2,5-di-tert.-butyl-4-hydroxy-anisole, 3,5-di-tert.-butyl-4-hydroxy-anisole, 3,5-di-tert.-butyl-4-hydroxyphenyl stearate and bis-(3,5-di-tert.-butyl-4-hydroxyphenyl)adipate.

1.3 Hydroxylated thiodiphenyl ethers, such as for example, 2,2'-thio-bis-(6-tert.-butyl-4-methylphenol), 2,2'-thio-bis(4-octylpenol), 4,4'-thio-bis-(6-tert.-butyl-3-methylphenol), 4,4'-thio-bis-(3,6-di-sec.-amylphenol), 4,4'-thio-bis-(6-tert.-butyl-2-methylphenol) and 4,4'-bis-(2,6-dimethyl-4-hydroxyphenyl) disulfide.

1.4 Alkylidene-bisphenols, such as, for example, 2,2'-methylene-bis-(6-tert.-butyl-4-methylphenol), 2,2'-methylene-bis-(6-tert.-butyl-4-ethylphenol), 4,4'-methylene-bis-(6-tert.-butyl-2-methylphenol, 4,4'-methylene-bis-(2,6-di-tert.-butylphenol), 2,6-di(3-tert.-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol, 2,2'-methylene-bis-[4-methyl-6-(α-methylcyclohexyl)-phenol], 1,1-bis(3,5-dimethyl-2-hydroxyphenyl)-butane, 1,1-bis-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-butane, 2,2-bis-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propane, 1,1,3-tris-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-butane, 2,2-bis-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercaptobutane, 1,1,5,5-tetra-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-pentane and ethylene glycol bis-[3,3-bis-(3-tert.-butyl-4-hydroxyphenyl)-butyrate].

1.5 O-, N- and S-benzyl compounds, such as for example, 3,5,3',5'-tetra-tert.-butyl-4,4'-dihydroxydibenzyl ether, octadecyl 4-hydroxy-3,5-dimethylbenzyl-mercaptoacetate, tris-(3,5-di-tert.-butyl-4-hydroxybenzyl)-amine and bis-(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl) dithioterephthalate.

1.6 Hydroxybenzylated malonates, such as for example, dioctadecyl 2,2-bis-(3,5-di-tert.-butyl-2-hydroxybenzyl)-malonate dioctadecyl 2-(3-tert.-butyl-4-hydroxy-5-methylbenzyl)-malonate, di-dodecylmercapto-ethyl 2,2-bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-malonate and di-[4-(1,1,3,3-tetramethylbutyl)-phenyl] 2,2-bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-malonate.

1.7 Hydroxybenzyl-aromatic compound, such as, for example, 1,3,5-tri-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, 1,4-di-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene and 2,4,6-tri-(3,5-di-tert.butyl-4-hydroxybenzyl)-phenol.

1.8 s-Triazine compounds, such as, for example 2,4-bis-octylmercapto-6-(3,5-di-tert.-butyl-4-hydroxy-anilino)-s-triazine, 2-octylmercapto-4,6-bis-(3,5-di-tert.-butyl-4-hydroxy anilino)-s-triazine, 2-octylmercapto-4,6-bis-(3,5-di-tert.-butyl-4-hydroxyphenoxy)-s-triazine, 2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxyphenoxy)-s-triazine, 2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenylethyl)-s-triazine and 1,3,5-tris-(3,5-di-tert.-butyl-4-hydroxybenzyl)isocyanurate.

1.9 Amides of β(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionic acid, such as, for example, 1,3,5-tris-(3,5-di-tert.-butyl-4-hydroxyphenyl-propionyl)-hexahydro-s-triazine and N,N'-di-3,5-di-tert.-butyl-4-hydroxyphenyl-propionyl)-hexamethylenediamine, N,N'-bis-β-(3,5-di-t-butyl-4-hydroxyphenyl)-propionyl-hydrazine.

1.10 Esters of β-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionic acid with monohydric or polyhydric alcohols, such as for example, with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, diethylene glycol, thiodiethylene glycol, neopentylglycol, pentaerythritol, 3-thiaundecanol, 3-thia-pentadecanol, trimethylhexnediol, trimethylolethane, trimethylolpropane, tris-hydroxyethyl isocyanurate and 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo-[2.2.2]octane.

1.11 Esters of β-(5-tert.-butyl-4-hydroxy-3-methylphenyl)propionic acid with monohydric or polyhydric alcohols, such as for example, with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, diethylene glycol, thiodiethylene glycol, neopentylglycol, pentaerythritol, 3-thia-undecanol, 3-thia-pentadecanol, trimethylhexanediol, trimethylolethane, trimethylolpropane, tris-hydroxyethyl isocyanurate and 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.

1.12 Esters of 3,5-di-tert.-butyl-4-hydroxyphenylacetic acid with monohydric or polyhydric alcohols, such as for example, with methanol, ethanol, octadecanol, 1,6-hexandiol, 1,9-nonanediol, ethylene glycol, 1,2-propenediol, diethylene glycol, thio-diethylene glycol, neopentylglycol, pentaerythritol, 3-thiaundecanol, 3-thia-pentadecanol, trimethylhexanediol, trimethylolethane, trimethylolpropane, tris-hydroxyethyl isocyanurate and 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]-octane especially the tetrakis ester of pentaerythritol.

1.13 Benzylphosphonates, such as, for example, dimethyl 3,5 di-tert.-butyl-4-hydroxybenzylphosphonate, diethyl 3,5-di-tert.-butyl-4-hydroxybenzylphosphonate, dioctadecyl 3,5-di-tert.-butyl-4-hydroxybenzylphosphonate and dioctadecyl 5-tert.-butyl-4-hydroxy-3-methylbenzylphosphonate.

2. LIGHT-STABILIZERS

2.1 Esters of optionally substituted benzoic acids, e.g., 3,5-di-tert.-butyl-4-hydroxybenzoic acid, 2,4-di-tert.-butylphenyl ester or -octadecyl ester or 2-methyl-4,6-di-tert.-butylphenyl ester.

2.2 Sterically hindered amines, e.g., 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis-(2,2,6,6-tetramethylpiperidyl) sebacate, bis-(1,2,2,6,6-pentamethylpiperidyl) 2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)malonate or 3-n-octyl-7,7,9,9-trimethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione.

2.3 Oxalic acid diamides, e.g., 4,4'-di-octyloxy-oxanilide, 2,2'-di-octyloxy-5,5'-di-tert.-butyl-oxanilide, 2,2'-di-dodecyloxy-5,5'-di-tert.-butyl-oxanilide, 2-ethoxy-2'-ethyl-oxanilide, N,N'-bis-(3-dimethyl-aminopropyl)-oxalamide, 2-ethoxy-5-tert.-butyl-2'-ethyl-oxanilide and the mixture thereof with 2-ethoxy-2'-ethyl-5,4'-di-tert.-butyl-oxanilide, or mixtures of ortho-and para-methoxy- as well as of o- and p-ethoxy-disubstituted oxanilides.

3. Metal deactivators, e.g., oxanilide, isophthalic acid dihydrazide, sebacic acid-bis-phenylhydrazide, bis-benzylideneoxalic acid dihydrazide, N,N'-diacetal-adipic acid dihydrazide, N,N'-bis-salicyloyl-oxalic acid dihydrazide, N,N'-bis-salicyloylhydrazine, N,N'-bis-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)-hydrazine, N-salicyloyl, N-salicyloyl-N'-salicylalhydrazine, 3-salicyloyl-amino-1,2-4-triazole or N,N'-bis-salicyloyl-thiopropionic acid dihydrazide.

4. Basic co-stabilizers, e.g., alkali metal salts and alkaline-earth metal salts of higher fatty acids, for example Ca-stearate, Zn-stearate, Mg-behenate, Na-ricinoleate or K-palmitate.

5. Nucleation agents, e.g., 4-tert.-butylbenzoic acid, adipic acid or diphenylacetic acid.

6. Phosphites and phosphonites, such as, for example, triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites, tri-(nonyl-phenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite and 3,9-isodecyloxy-2,4,8,10-tetraoxa-3,9-diphospha-[5.5]-undecane and tetra(2,4-di-tert-butylphenyl) diphenylene-4,4'-bis(phosphonite).

Other additives that can be incorporated in the stabilized compositions are thiosynergists such as dilauryl thiodiproprionate, lubricants such as stearyl alcohol, fillers, asbestos, kaolin, talc, glass fibers, pigments, optical brighteners, flameproofing agents and antistatic agents.

The combination of a hindered amine light stabilizer and an instant benzotriazole UV light stabilizer provides a particularly beneficial solution to the combined goal of gloss retention and delamination resistance in metallic thermoset acrylic enamels and in metallic thermoplastic acrylic lacquers for automotive topcoats.

The hindered amine light stabilizers protect the thermoset acrylic enamels and thermoplastic acrylic lacquers against loss of gloss on weathering, but do not act as UV light screens. Accordingly, UV light can pass through the acrylic topcoat in the absence of a UV light absorber and failure of the epoxy ester primer surface beneath the topcoat can then occur.

The addition of an instant benzotriazole UV light absorber into the acrylic topcoat prevents UV light from passing through and causing deterioration of the primer surface beneath.

Thus, a combination of hindered amine with benzotriazole in the acrylic topcoat provides both gloss retention and resistance to delamination for the metallic acrylic topcoats.

The hindered amine is effective in this composition in preventing gloss at the 0.1 to 5%, preferably 0.5 to 2%, and most preferably at the 0.5 to 1% by weight level based on the acrylic topcoat resin.

The instant benzotriazole is effective in preventing delamination of the acrylic topcoat at the 0.1 to 5%, preferably 0.5 to 2%, and most preferably at the 0.5 to 1% by weight level based on the acrylic topcoat resin.

The hindered amine light stabilizers useful in this invention are described by the general formula ##STR7## wherein q is 1 or 2, p is 2 to 14, G₁, G₂, G₃ and G₄ are independently alkyl; or G₁ and G₃ together are alkylene or each are carboalkoxy or carbophenethoxy; or G₁ and G₂ or G₃ and G₄, independently of one another, together are alkylene or azaalkylene,

if q is 1, m is hydrogen, hydroxyl, oxyl, optionally substituted alkyl, alkenyl, alkynyl, aralkyl, alkanoyl, alkenoyl, benzoyl, glycidyl or --CH₂ CHOHZ where Z is hydrogen, methyl or phenyl,

if q is 2, M is alkylene, alkenylene, alkynylene, arylenedialkylene, the group --(CH₂)₂ OOCR₁₈ COO(CH₂)₂ -- or the group --CH₂ OOOCR₁₉ COOCH₂ -- where R₁₈ is alkylene and R₁₉ is alkylene, xylylene or cyclohexylene,

M₁ has the meaning of M where q is 1,

L is a divalent organic radical which supplements the N-containing ring to form a 5 to 7 membered ring, or is two monovalent organic radicals, and

L₁ is a divalent organic radical which supplements the N-containing ring to form a 5 to 7 membered ring and which additionally provides a linking group to other hindered amine moieties.

Among the hindered amines useful in this invention are compounds having the formula ##STR8## where G₅ is hydrogen, alkyl or phenethyl and M₂ is hydrogen, hydroxyl, oxyl, alkyl, 2-methoxyethyl, alkenyl or propargyl.

The hindered amine light stabilizers useful in the instant invention are in particular 2,2,6,6-tetraalkylpiperidine compounds which contain a group of the formula (I) ##STR9## in which R is hydrogen or methyl.

The light stabilisers to be used according to the invention include in particular the following classes of compounds:

(a) Light stabilisers of the formula (II) ##STR10## in which n is a number from 1-4 inclusive, preferably 1 or 2; R is as defined under the formula (I); R₁ is hydrogen, oxyl, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl, C₃ -C₅ alkenoyl, glycidyl, a group --CH₂ CH(OH)--Z wherein Z is hydrogen, methyl or phenyl, with R₁ preferably being hydrogen, C₁ -C₁₂ alkyl, allyl, benzyl, acetyl or acryloyl; and R₂ when n is 1 is hydrogen, C₁ -C₁₈ alkyl optionally interrupted by one or more oxygen atoms, cyanoethyl, benzyl, glycidyl, a monovalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acid, or a carbamic acid or of a phosphorus-containing acid, or a monovalent silyl radical, preferably a radical of an aliphatic carboxylic acid having 2-18 C atoms, of a cycloaliphatic carboxylic acid having 5-12 C atoms or of an aromatic carboxylic acid having 7-15 C atoms; R₂ when n is 2 is C₁ -C₁₂ alkylene, C₄ -C₁₂ alkenylene, xylylene, a bivalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid, of dicarbamic acid or of a phosphorus-containing acid, or a bivalent silyl radical, preferably a radical of an aliphatic dicarboxylic acid having 2-36 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8-14 C atoms, or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 C atoms; R₂ when n is 3 is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid, of an aromatic tricarbamic acid or of a phosphorus-containing acid, or a trivalent silyl radical; and R₂ when n is 4 is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid.

If any substituents are C₁ -C₁₂ alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.

As C₁ -C₁₈ alkyl, R₁ or R₂ can be for example the groups given above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.

When R₁ is C₃ -C₈ alkenyl, it can be for example 1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl or 4-tert-butyl-2-butenyl.

As C₃ -C₈ alkynyl, R₁ is preferably propargyl.

R₁ is C₇ -C₁₂ aralkyl is in particular phenethyl or especially benzyl.

As C₁ -C₈ alkanoyl, R₁ is for example formyl, propionyl, butyryl, octanoyl but preferably acetyl, and as C₃ -C₅ alkenoyl, R₁ is particularly acryloyl.

If R₂ is a monovalent radical of a carboxylic acid, it is for example a radical of acetic acid, stearic acid, salicylic acid, methacrylic acid, maleic acid, benzoic acid or β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid.

If R₂ is a bivalent radical of a dicarboxylic acid, it is for example a radical of adipic acid, suberic acid, sebacic acid, phthalic acid, dibutylmalonic acid, dibenzylmalonic acid or butyl-(3,5di-tert-butyl-4-hydroxybenzyl)-malonic acid, or bicycloheptenedicarboxylic acid.

If R₂ is a trivalent radical of a tricarboxylic acid, it is for example a radical of trimellitic acid or of nitrilotriacetic acid.

If R₂ is a tetravalent radical of a tetracarboxylic acid, it is for example a radical of pyromellitic acid.

If R₂ is a bivalent radical of a dicarbamic acid, it is for example a radical of hexamethylenedicarbamic acid or of 2,4-toluylenedicarbamic acid.

The following compounds are examples of polyalkylpiperidine light stabilisers of this class:

(1) 4-hydroxy-2,2,6,6-tetramethylpiperidine,

(2) 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine,

(3) 1-benzyl-4-hydroxy-2,2,6,6-tetramethylpiperidine,

(4) 1-(4-tert-butyl-2-butenyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine,

(5) 4-stearoyloxy-2,2,6,6-tetramethylpiperidine,

(6) 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine,

(7) 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine,

(8) 1,2,2,6,6-pentamethylpiperidin-4-yl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate,

(9) 1-benzyl-2,2,6,6-tetramethyl-4-piperidinylmaleinate,

(10) (di-2,2,6,6-tetramethylpiperidin-4-yl)-adipate

(11) (di-2,2,6,6-tetramethylpiperidin-4-yl)-sebacate,

(12) (di-1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl)-sebacate,

(13) (di-1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl)-phthalate,

(14) 1-propargyl-4-β-cyanoethyloxy-2,2,6,6-tetramethyl-piperidine,

(15) 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate,

(16) trimellitic acid-tri-(2,2,6,6-tetramethylpiperidin-4-yl) ester,

(17) 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine,

(18) dibutyl-malonic acid-di-(1,2,2,6,6-pentamethylpiperidin-4-yl) ester,

(19) butyl-(3,5-di-tert-butyl-4-hydroxybenzyl)-malonic acid-di-(1,2,2,6,6-pentamethylpiperidin-4-yl) ester,

(20) dibenzyl-malonic acid-di-(1,2,2,6,6-pentamethylpiperidin-4-yl) ester,

(21) dibenzyl-malonic acid-di-(1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) ester,

(22) hexane-1',6'-bis-(4-carbamoyloxy-1-n-butyl-2,2,6,6-tetramethylpiperidine),

(23) toluene-2',4'-bis-(4-carbamoyloxy-1-n-propyl-2,2,6,6-tetramethylpiperidine),

(24) dimethyl-bis-(2,2,6,6-tetramethylpiperidine-4-oxy)-silane,

(25) phenyl-tris-(2,2,6,6-tetramethylpiperidine-4-oxy)-silane,

(26) tris-(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)-phosphite,

(27) tris-(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)-phosphate, and

(28) phenyl-[bis-(1,2,2,6,6-pentamethylpiperidin-4-yl)]-phosphonate.

(b) Light stabilisers of the formula (III) ##STR11## in which n is the number 1 or 2; R is as defined under the formula I; R₁ is as defined under (a); R₃ is hydrogen, C₁ -C₁₂ alkyl, C₅ -C₇ cycloalkyl, C₇ -C₈ aralkyl, C₂ -C₁₈ alkanoyl, C₃ -C₅ alkenoyl or benzoyl; and R₄ when n is 1 is hydrogen, C₁ -C₁₈ alkyl, C₅ -C₇ cycloalkyl, C₂ -C₈ alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or it is glycidyl, a group of the formula --CH₂ --CH(OH)--Z or of the formula --CONH--Z wherein Z is hydrogen, methyl or phenyl; or R₄ when n is 2 is C₂ -C₁₂ alkylene, C₆ -C₁₂ arylene, xylilene, a --CH₂ --CH(OH)--CH₂ group, or a group --CH₂ --CH(OH)--CH₂ --O--X--O--CH₂ --CH(OH)--CH.sub. 2 -- wherein X is C₂ -C₁₀ alkylene, C₆ -C₁₅ arylene or C₆ -C₁₂ cycloalkylene; or, provided that R₃ is not alkanoyl, alkenoyl or benzoyl, R₄ can also be a bivalent radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group --CO--; or R₃ and R₄ together when n is 1 can be the cyclic radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid.

If any substituents are C₁ -C₁₈ alkyl, they are as already defined under (a).

If any substituents are C₅ -C₇ cycloalkyl, they are in particular cyclohexane.

As C₇ -C₈ aralkyl, R₃ is particularly phenethyl or above all benzyl.

As C₂ -C₁₈ alkanoyl, R₃ is for example propionyl, butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl but preferably acetyl; and as C₃ -C₅ alkenoyl, R₃ is in particular acryloyl.

If R₄ is C₂ -C₈ alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, it is for example 1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl, 2,2-dicyanovinyl, 1-methyl-2-cyano-2-methoxycarbonyl-vinyl or 2,2-diacetylaminovinyl.

If any substituents are C₂ -C₁₂ alkylene, they are for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.

If any substituents are C₆ -C₁₅ arylene, they are for example o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.

As C₆ -C₁₂ cycloalkylene, X is especially cyclohexylene.

The following compounds are examples of polyalkylpiperidine light stabilisers of this class:

(29) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diamine,

(30) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diacetamide

(31) 1-acetyl-4-(N-cyclohexylacetamido)-2,2,6,6-tetramethyl-piperidine,

(32) 4-benzylamino-2,2,6,6-tetramethylpiperidine,

(33) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-N,N'-dibutyl-adipamide,

(34) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-N,N'-dicyclohexyl-(2-hydroxypropylene),

(35) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-p-xylylene-diamine,

(36) the compound of the formula ##STR12## (37) 4-(bis-2-hydroxyethyl)-amino-1,2,2,6,6-pentamethylpiperidine, (38) 4-(3-methyl-4-hydroxy-5-tert-butyl-benzoic acidamido)-2,2,6,6-tetramethylpiperidine,

(39) 4-methacrylamido-1,2,2,6,6-pentamethylpiperidine, and

(40) α-cyano-β-methyl-β-[N-(2,2,6,6-tetramethylpiperidin-4-yl)]-amino-acrylic acid methyl ester.

(c) Light stabilisers of the formula (IV) ##STR13## in which n is the number 1 or 2; R is as defined under the formula (I); R₁ is as defined under (a); and R₅ when n is 1 is C₂ -C₈ alkylene or hydroxyalkylene or C₄ -C₂₂ acyloxyalkylene; and R₅ when n is 2 is the group (--CH₂)₂ C(CH₂ --)₂.

If R₅ is C₂ -C₈ alkylene or hydroxyalkylene, it is for example ethylene, 1-methyl-ethylene, propylene, 2-ethylpropylene or 2-ethyl-2-hydroxymethylpropylene.

As C₄ -C₂₂ acyloxyalkylene, R₅ is for example 2-ethyl-2-acetoxymethyl-propylene.

The following compounds are examples of polyalkylpiperidine light stabilisers of this class:

(41) 9-aza-8,8,10,10-tetramethyl-1,5-dioxaspiro-[5.5]undecane,

(42) 9-aza-8,8,10,10-tetramethyl-3-ethyl-1,5-dioxaspiro [5.5]decane,

(43) 8-aza-2,7,7,8,9,9-hexamethyl-1,4-dioxyspiro[4.5]decane,

(44) 9-aza-3-hydroxymethyl-3-ethyl-8,8,9,10,10-pentamethyl-1,5-dioxaspiro[5.5]undecane,

(45) 9-aza-3-ethyl-3-acetoxymethyl-9-acetyl-8,8,10,10-tetramethyl-1,5-dioxaspiro[5.5]undecane, and

(46) 2,2,6,6-tetramethylpiperidine-4-spiro-2'-(1',3'-dioxane)-5'-spiro-5"-(1",3"-dioxane)-2"-spiro-4'"-(2'",2'",6'",6'"-tetramethylpiperidine).

(d) Light stabilisers of the formula (V) ##STR14## in which n is the number 1 or 2; R is as defined under the formula (I); R₁ is as defined under (a); R₆ is hydrogen, C₁ -C₁₂ alkyl, allyl, benzyl, glycidyl or C₂ -C₆ alkoxyalkyl; and R₇ when n is 1 is hydrogen, C₁ -C₁₂ alkyl, C₃ -C₅ alkenyl, C₇ -C₉ aralkyl, C₅ -C₇ cycloalkyl, C₂ -C₄ hydroxyalkyl, C₂ -C₆ alkoxyalkyl, C₆ -C₁₀ aryl, glycidyl, a group of the formula --(CH)--COO--Q or of the formula --(CH₂)_(m) --O--CO--Q wherein m is 1 or 2, and Q is C₁ -C₄ alkyl or phenyl; or R₇ when n is 2 is C₂ -C₁₂ alkylene, C₆ -C₁₂ arylene, a group --CH₂ --CH(OH)--CH₂ --O--X--O--CH₂ --CH(OH)--CH₂ -- wherein X is C₂ -C₁₀ alkylene, C₆ -C₁₅ arylene or C₆ -C₁₂ cycloalkylene, or a group --CH₂ CH(OZ') CH₂ --(OCH₂ --CH(OZ')CH₂)₂ -- wherein Z' is hydrogen, C₁ -C₁₈ alkyl, allyl, benzyl, C₂ -C₁₂ alkanoyl or benzoyl.

If any substituents are C₁ -C₁₂ alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.

As C₁ -C₁₈ alkyl, Z' can be for example the groups stated above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.

If any substituents are C₂ -C₆ alkoxyalkyl, they are for example methoxymethyl, ethoxymethyl, propoxymethyl, tert-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl, tert-butoxyethyl, isopropoxyethyl or propoxypropyl.

If R₇ is C₃ -C₅ alkenyl, it is for example 1-propenyl, allyl, methallyl, 2-butenyl or 2-pentenyl.

As C₇ -C₉ aralkyl, R₇ is in particular phenethyl or above all benzyl; and as C₅ -C₇ cycloalkyl, R₇ is especially cyclohexyl.

If R₇ is C₂ -C₄ hydroxyalkyl, it is for example 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl or 4-hydroxybutyl.

As C₆ -C₁₀ aryl, R₇ is in particular phenyl, or α- or β-naphthyl which is unsubstituted or substituted by halogen or C₁ -C₄ alkyl.

If R₇ is C₂ -C₁₂ alkylene, it is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.

If R₇ is C₆ -C₁₂ arylene, it is for example o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.

If Z' is C₂ -C₁₂ alkanoyl, it is for example propionyl, butyryl, octanoyl, dodecanoyl or preferably acetyl.

As C₂ -C₁₀ alkylene, C₆ -C₁₅ arylene or C₆ -C₁₂ cycloalkylene, X has the meaning given under (b).

The following compounds are examples of polyalkylpiperidine light stabilisers of this class:

(47) 3-benzyl-1,3,8-triaza-7,7,9,9-tetramethylspiro[4.5]decane-2,4-dione,

(48) 3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiro[4.5]decane-2,4-dione,

(49) 3-allyl-1,3,8-triaza-1,7,7,9,9-pentamethylspiro[4.5]decane-2,4-dione,

(50) 3-glycidyl-1,3,8-triaza-7,7,8,9,9-pentamethylspiro[4.5]decane-2,4-dione,

or the compounds of the following formulae: ##STR15##

(e) Light stabilisers of the formula (IV) ##STR16## in which n is the number 1 or 2, and R₈ is a group of the formula ##STR17## in which R is as defined under the formula (I), R₁ is as defined under (a), Y is --O-- or --NR₁₁ --, A is C₂ -C₆ alkylene; and m is the number 0 or 1; R₉ is the groups R₈, NR₁₁ R₁₂, --OR₁₃, --NHCH₂ OR₁₃ or --N(CH₂ OR₁₃)₂ ; R₁₀ when n is 1 is the groups R₈ or R₉, and R₁₀ when n is 2 is the group --Y--Q--Y-- wherein Q is C₂ -C₆ alkylene optionally interrupted by --N(R₁₄)--; R₁₁ is C₁ -C₁₂ alkyl, cyclohexyl, benzyl or C₁ -C₄ hydroxyalkyl, or a group of the formula ##STR18## R₁₂ is C₁ -C₁₂ alkyl, cyclohexyl, benzyl or C₁ -C₄ hydroxyalkyl; R₁₃ is hydrogen, C₁ -C₁₂ alkyl or phenyl; and R₁₄ is hydrogen or the group --CH₂ OR₁₃ ; or R₁₁ and R₁₂ together are C₄ -C₅ alkylene or oxaalkylene, or R₁₁ and R₁₂ are each a group of the formula ##STR19##

If any substituents are C₁ -C₁₂ alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.

If any substituents are C₁ -C₄ hydroxyalkyl, they are for example 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl or 4-hydroxybutyl.

If A is C₂ -C₆ alkylene, it is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene or hexamethylene.

If R₁₁ and R₁₂ together are C₄ -C₅ alkylene or oxaalkylene, this is for example tetramethylene, pentamethylene or 3-oxapentamethylene.

The compounds of the following formulae are examples of polyalkylpiperidine light stabilisers of this class: ##STR20##

(f) Light stabilizers of the formula (VII) ##STR21## in which n is the number 1 or 2; R is as defined under the formula (I); and R₁₄ when n is 1 is C₄ -C₁₈ alkyl, C₇ -C₁₂ aralkyl, the group --CO--R₁₅, or C₁ -C₄ alkyl which is substituted by --CN, --COOR₁₆, --OH, --OCOR₁₇ or ##STR22## wherein R₁₅ is C₁ -C₁₂ alkyl, C₂ -C₄ alkenyl or phenyl, R₁₆ is C₁ -C₁₈ alkyl, R₁₇ is C₁ -C₁₈ alkyl, C₂ -C₁₀ alkenyl, cyclohexyl, benzyl or C₆ -C₁₀ aryl; or R₁₄ when n is 2 is C₄ -C₁₂ alkylene, 2-butenylene-1,4,xylylene, the group --(CH₂)₂ --OOC--R₁₈ --COO--(CH₂)₂ -- or the group --CH₂ --OOC--R₁₉ --COO--CH₂ -- wherein R₁₈ is C₂ -C₁₀ alkylene, phenylene or cyclohexylene, and R₁₉ is C₂ -C₁₀ alkylene, xylylene or cyclohexylene.

If any substituents are C₁ -C₁₂ alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.

Any substituents which are C₁ -C₁₈ alkyl can be for example the groups mentioned above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.

If any groups are C₂ -C₁₀ alkylene, these are in particular ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene or decamethylene.

As C₄ -C₁₈ alkyl, R₁₄ is for example n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, 1,1-dimethyl-2-tert-butylethyl, n-nonyl, n-decyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.

If R₁₄ is a C₁ -C₄ alkyl group substituted by --CN, it is for example cyanomethyl, cyanoethyl, 3-cyano-n-propyl or 4-cyano-n-butyl.

If R₁₄ is C₄ -C₁₂ alkylene, it is for example 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.

If R₁₄ is C₇ -C₁₂ aralkyl, it is in particular penethyl, p-methyl-benzyl or especially benzyl.

As C₂ -C₄ alkenyl, R₁₅ is for example vinyl, 1-propenyl, allyl, methallyl or 2-butenyl.

As C₂ -C₁₀ alkenyl, R₁₇ is for example the groups mentioned for R₁₅ as alkenyl, and in addition for example crotyl, 2-hexenyl, 2-octenyl or 2-decenyl.

If R₁₇ is C₆ -C₁₀ aryl, it is for example phenyl which is unsubstituted or substituted in the o- or p-position by methyl, ethyl, isopropyl, n-butyl or tert-butyl.

The following compounds are examples of polyalkylpiperidine light stabilisers of this class:

(60) bis-[β-(2,2,6,6-tetramethylpiperidino)-ethyl]-sebacate,

(61) α-(2,2,6,6-tetramethylpiperidino)-acetic acid-n-octyl ester, and

(62) 1,4-bis-2,2,6,6-tetramethylpiperidino)-2-butene.

(g) Light stabilizers of the formula (VIII) ##STR23## in which Q is --N(R₃)-- or --O--; E is C₁ -C₃ alkylene, the group --CH₂ --CH(R₄)--O-- wherein R₄ is hydrogen, methyl or phenyl, the group --(CH₂)₃ --NH-- or a single bond; R is hydrogen or methyl; R₁ is hydrogen, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl, C₃ -C₅ alkenoyl or glycidyl; R₂ is hydrogen or C₁ -C₁₈ alkyl; R₃ is hydrogen, C₁ -C₁₈ alkyl, C₅ -C₇ cycloalkyl, C₇ -C₁₂ aralkyl, cyanoethyl, C₆ -C₁₀ aryl, the group --CH₂ --CH(R₄)--OH wherein R₄ has the meaning defined above, a group of the formula ##STR24## or a group of the formula ##STR25## wherein G can be C₂ -C₆ alkylene or C₆ -C₁₂ arylene; or R₃ is a group --E--CO--NH--CH₂ --OR₂.

If any substituents are C₁ -C₁₈ alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.

If any substituents are C₇ -C₁₂ aralkyl, they are for example phenethyl or in particular benzyl.

If R₁ is C₃ -C₈ alkenyl, it can be for example 1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl or 4-tert-butyl-2-butenyl.

As C₃ -C₈ alkynyl, R₁ is preferably propargyl. As C₁ -C₈ alkanoyl, R₁ is for example formyl, propionyl, butyryl, octanoyl but preferably acetyl; and as C₃ -C₅ alkenoyl, R₁ is especially acryloyl.

As C₅ -C₇ cycloalkyl, R₃ is in particular cyclohexyl.

As C₆ -C₁₀ aryl, R₃ is particularly phenyl, or α- or β-naphthyl which is unsubstituted or substituted with halogen or C₁ -C₄ alkyl. As C₁ -C₃ alkylene, E is for example methylene, ethylene or propylene.

As C₂ -C₆ alkylene, G is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene or hexamethylene; and as C₆ -C₁₂ arylene, G is o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.

The following compounds are examples of polyalkylpiperidine light stabilizers of this class:

(63) N-hydroxymethyl-N'-2,2,6,6-tetramethylpiperidin-4-yl-urea,

(64) N-methoxymethyl-N'-2,2,6,6-tetramethylpiperidin-4-yl-urea,

(65) N-methoxymethyl-N'-n-dodecyl-N'-2,2,6,6-tetramethyl-piperidin-4-yl-urea, and

(66) O-(2,2,6,6-tetramethylpiperidin-4-yl)-N-methoxymethyl-urethane.

(f) Polymeric compounds of which the recurring structural unit contains a polyalkylpiperidine radical of the formula (I), especially polyesters, polyethers, polyamides, polyamines, polyurethanes, polyureas, polyaminotriazines, poly(meth)acrylates or poly(meth)acrylamides, and copolymers thereof which contain such radicals.

The compounds of the following formulae, wherein m is a number from 2 to about 200 inclusive, are examples of polyalkylpiperidine light stabilizers of this class. ##STR26##

It is also possible to use polyalkylpiperidine derivatives of the classes (a)-(f) which form chemical bonds with the binder of the lacquer or enamel. This is the case when the polyalkylpiperidine derivative possesses a reactive group suitable for this purpose, for example a glycidyl group or a methylol group.

Examples of such compounds are the polyalkylpiperidine derivatives of the class (g) containing methylol or methylol ether groups.

Provided the polyalkylpiperidine derivatives are basic compounds, they can form salts with acids. Suitable acids are for example inorganic acids or organic carboxylic, sulfonic, phosphonic or phosphinic acids, such as hydrochloric acid, boric acid, phosphoric acid, acetic acid, salicyclic acid, toluenesulfonic acid or benzenephosphonic acid.

The polyalkylpiperidine compounds can form complexes with complex-forming metal compounds, for example with zinc-II-acetate, cobalt-II-acetylacetonate, nickel-II-acetylacetonate, aluminum-III-acetylacetonate, nickel-II-benzoate or aluminum-III-benzoylacetonate.

The following examples are presented for the purpose of illustration only and are not to be construed to limit the nature or scope of the instant invention in any manner whatsoever.

EXAMPLE 1 2,4-Di-(α,α-dimethylbenzyl)phenol

This intermediate was made by the general procedure of U.S. Pat. No. 2,714,120 by reacting a mixture of 705.8 grams (7.5 moles) of phenol with 1772.7 grams (15 moles) of α-methylstyrene in the presence of 25.7 grams (0.135 moles) of p-toluenesulfonic acid monohydrate catalyst. This mixture was heated under nitrogen at 140° C. for 2.5 hours. The reaction mixture was cooled to 110° C. and 1125 ml of toluene was added. After washing the resulting solution at 80° C. with 750 ml of an aqueous solution of 37.5 grams of sodium carbonate and 75 grams of sodium chloride, the organic phase was washed thrice with 1000 ml of aqueous sodium chloride solution; then dried over anhydrous sodium sulfate; filtered and vacuum distilled. The above-named product was obtained as the main fraction boiling at 172°-175° C./0.15-0.18 mm Hg in a yield of 1229.8 grams (49.6% of theory). The product melted 63° -65° C.

EXAMPLE 2 2-Nitro-2'-hydroxy-3',5'-di(α,α-dimethylbenzyl)azobenzene Acid Coupling Process

To a 2-liter, 3-necked flask fitted with a stirrer and thermometer was charged 90.6 grams of a 26% aqueous solution of technical naphthalenesulfonic acid, 1.9 grams of Triton X-207 (non-ionic surfactant), 5.6 grams of Conco AAS-90F (sodium dodecylbenzenesulfonate) and 90 ml of water. The mixture was warmed to 40° C. and then 116.5 grams of 2,4-di(α,α-dimethylbenzyl)phenol, preheated to 90° C., was slowly added to the mixture with vigorous stirring keeping the temperature at 40° C.

A cold solution of o-nitrobenzenediazonium chloride, prepared from 49.8 grams (0.36 mole) of o-nitroaniline and 24.9 grams (0.36 mole) of sodium nitrite in concentrated aqueous hydrochloric acid solution at a temperature of -5° to 0° C., was added dropwise into the reaction mixture over a 3-hour period. The resulting deep red to black reaction mixture was kept at 40° C. overnight. The temperature was raised to 65° C. for 1 hour; then the 95° C. for another 30 minutes. After cooling to 85° C., the reaction mixture was isolated as a resinous, viscous, deep red-black mass by filtration.

The crude product was triturated with four 200 ml portions of hot (75° C.) water; then with 400 ml of methanol overnight; and stirred in a blender with another 400 ml of methanol to yield a fine granular product. The dark red o-nitroazobenzene intermediate named above was obtained in a yield of 81.9 grams (48.4% of theory) and melted at 139°-141° C. Thin layer chromatography indicated a homogeneous product with an R_(f) value of 0.61 on silicagel (3 cyclohexane:1 ethyl acetate).

EXAMPLE 3 2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)-phenyl]-2H-benzotriazole

To a 5-liter 3-necked flask fitted with a stirrer, thermometer, reflux condenser and nitrogen inlet was charged 386 grams (0.805 mol) of the o-nitroazobenzene intermediate of Example 2 and 1200 ml of toluene. To the resulting solution was added 240 ml of isopropanol and 240 ml of water. A nitrogen atmosphere was imposed and 160 ml of 50.1% aqueous sodium hydroxide was added. A flask containing 158.2 gram (2.42 gram-atoms) of zinc was connected to the reaction flask by Gooch rubber tubing and the zinc dust was added portionwise to the reaction mixture over a 90-minute period. The zinc was added at such a rate to keep the internal temperature between 40° and 45° C. After the zinc was all added, the reaction mixture was heated for 1 hour at 40° C. and then for 3 hours at 70° C. The mixture was cooled to room temperature and acidified with 600 ml of concentrated hydrochloric acid.

The zinc sludge was removed by filtration. The product was contained in the organic layer, which was washed with four 340 ml portions of dilute hydrochloric acid, and then dried over anhydrous sodium sulfate. The organic solvent was removed in vacuo to yield a crude product as a viscous syrup which crystallized on standing.

The crude product was recrystallized first from 750 ml of ethyl acetate to give 225 grams (62.5% of theory) of light tan crystals. The product was further purified by recrystallization from 1000 ml of a 4:1 mixture of acetonitrile:ethyl acetate and then dissolved in 1250 ml of toluene. The toluene solution was extracted with 70% aqueous sulfuric acid to remove colored impurities before yielding 219.3 grams (60.9% theory) of slightly off white crystals melting at 140°-141° C. of the above named compound. (Compound 1).

Analysis: Calcd for C₃₀ H₂₉ N₃ O: C: 80.51; H,6.53; N:9.39. Found C: 80.53; H,6.54; N:9.51.

EXAMPLE 4 2-Nitro-2'-hydroxy-3',5'-di(α,α-dimethylbenzyl)azobenzene Alkaline Coupling Process

To a 500-ml 3-necked flask fitted with a stirrer, thermometer, pressure equalized addition funnel and nitrogen inlets and outlets were charged 13.5 grams (0.21 mole) of potassium hydroxide pellets and 10 ml of water. The resulting hot solution was diluted with 80 ml of methanol. After flushing with nitrogen, 16.5 grams (0.05 mole) of 2,4-di(α,α-dimethylbenzyl)phenol and 85 ml of methanol were added to give a clear solution which was then cooled to -4° C. A cold solution of o-nitrobenzenediazonium chloride in concentrated hydrochloric acid solution (42.9 grams=0.06 mole of diazonium solution) was added over a period of 15 minutes with rapid stirring while keeping the temperature between -2° and 0° C. The deep purple color of the azodye-phenoxide developed instantaneously as the diazonium solution was added. The resulting mixture was stirred for another 10 minutes at -1° to 1° C. The suspension was then acidified with 20 ml of glacial acetic acid over a 2-minute period at 1° to 3° C. The resulting brick red suspension was stirred for 15 minutes as the temperature was allowed to rise to ambient temperature and then filtered. The filter cake was washed with a cold solution of 40 grams ice in 160 ml of methanol and then with 1800 ml of water.

The bright red crude product was vacuum dried at 60° C. at 75 mm Hg for 16 hours yielding 22.7 grams of of material melting at 135°-140° C. Spectrophotometric assay indicated 86.7% purity giving a calculated yield of pure compound of 82% of theory.

The crude product was conveniently recrystallized from hot n-butanol using 5 ml per gram to give 95% recovery of pure product melting at 147°-148° C.

EXAMPLE 4a 2-Nitro-2'-hydroxy-3',5'-di-(α,α-dimethylbenzyl)azobenzene

Using the general procedure of Example 4, 13.6 grams (0.34 mole) of sodium hydroxide pellets were dissolved in 145 ml of methanol followed by the addition of 16.5 grams (0.05 mole) of 2,4-di-(α,α-dimethylbenzyl)phenol and an additional 20 ml of methanol. The resulting solution was cooled to 2° C. Meanwhile a solution of o-nitrobenzenediazonium chloride was prepared by diazotizing a mixture of 8.3 grams (0.06 mole) of o-nitroaniline and 17.3 grams of concentrated hydrochloric acid and 6 ml of water with a solution of 4.3 grams of sodium nitrite in 8 ml of water. The diazonium solution was added gradually to the alkaline solution over a two-hour period at 2° C. The resulting deep purple reaction mixture was stirred for 30 minutes at 2° C., and then acidified with 20 ml of glacial acetic acid.

The bright red precipitate was isolated by filtration and washed successively with 3×50 ml of methanol and then with 4×75 ml of water. The product was dried at 75° C. at 75 mm Hg yielding 21.6 grams of the title compound, melting at 140°-142° C. Spectrophotometric assay indicated the product to have 97% purity giving a calculated yield of pure material of 89% of theory.

EXAMPLE 5 2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole

When in following the general procedure of Example 3 an equivalent amount of 2-nitro-2'-hydroxy-3',5'-di(α,α-dimethylbenzyl)azobenzene prepared Example 4 was substituted for that prepared in Example 2, the above-named product was obtained in a yield of 80.2% of theory as very pale yellowish crystals melting at 139.5°-140° C. (Compound 1).

Analysis: Calcd for C₃₀ H₂₉ N₃ O: C: 80.51; H,6.53; N:9.39. Found C: 80.47; H,6.28; N:9.40.

EXAMPLES 6-8f Alkaline Coupling Process

When the alkaline coupling procedure of Example 4 was used with o-nitrobenzenediazonium chloride and a variety of phenols other than 2,4-di-(α,α-dimethylbenzyl)phenol, the yields of the corresponding o-nitroazobenzene products varied depending on the substitution in the phenol being coupled.

    ______________________________________                                                                    Yield (%) of                                                                   corresponding                                       Example                                                                               Phenol              o-nitroazobenzene                                   ______________________________________                                         6      2,4-di-tert-amyl    66                                                  7      2,4-di-tert-octyl   70(50).sup.a                                        7a     2,4-di-tert-octyl   47.sup.b                                            4      2,4-di-(α,α-dimethylbenzyl)                                                            82                                                  4a     2,4-di-(α,α-dimethylbenzyl)                                                            89.sup.c                                            8      2-(1-phenylethyl)-4-methyl                                                                         84.3                                                8a     4-methyl            56.sup.d                                            8b     2,4-di-n-octyl      56.sup.e                                            8c     2-methyl-4-α,α-dimethylbenzyl                                                          85*                                                 8d     2-α,α-dimethylbenzyl-4-methyl                                                          66.sup.f                                            8e     2-α,α-dimethylbenzyl-4-tert-butyl                                                      54                                                  8f     2-α,α-dimethylbenzyl-4-tert-octyl                                                      62                                                         control, no phenol  0.sup.g                                             ______________________________________                                          .sup.a Run by procedure of Example 4a with high alkali concentration.          Yield was 50% after purification. Nitrogen gas evolved = 48% of theory.        .sup.b Nitrogen gas evolved = 60% of theory.                                   .sup.c Run by procedure of Example 4a.                                         .sup.d Nitrogen gas evolved = 29% of theory.                                   .sup.e Coupling in acid medium gave only a 16-19% yield of product.            .sup.f Nitrogen gas evolved = 33% of theory.                                   .sup.g When no phenol was present some 67% of the theoretical amount of        nitrogen gas was evolved from the decomposition of the diazonium solution      *Yield was 47% when 4chloro-2-nitrobenzenediazonium chloride was coupled       with this phenol.                                                        

EXAMPLE 9 4-Chloro-2-nitro-2'-hydroxy-3',5'-di(α,α-dimethylbenzyl)azobenzene

When, using the general procedure of Example 2, an equivalent amount of the diazonium solution prepared from 4-chloro-2-nitroaniline was substituted for the diazonium solution prepared from 2-nitroaniline, the above-named compound was prepared in a yield of 47.3% as a very dark red solid.

EXAMPLE 10 5-Chloro-2-[2'-hydroxy-3',5'-di(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole

When, using the general procedure of Example 3, the amount of 4-chloro-2-nitro-2'-hydroxy-3',5'-di-(α,α-dimethylbenzyl)azobenzene was substituted for 2-nitro-2'-hydroxy-3',5'-di-(α,α-dimethylbenzyl)azobenzene, the above-named compound was prepared in a yield of 70.0% as light tan crystals melting at 160°-161° C. (Compound 2)

Analysis: Calcd for C₃₀ H₂₈ ClN₃ O: C: 74.45; H,5.86; N:8.72. Found C: 74.53; H,6.11; N:8.72.

EXAMPLE 11 Resistance to Loss of Benzotriazole Stabilizers

A number of 2-aryl-2H-benzotriazole light stabilizers were subjected to thermal gravimetric analysis both isothermally at 280° C. to indicate the time in minutes to reach 10%, 50% and 100% weight loss of the stabilizer as well as in a scanning mode at a heating rate of 10°(C.) per minute to ascertain the temperature at which 10% and 50% weight loss of stabilizer were observed.

Experimental data are given on Table A.

These results correlate closely with the resistance of the indicated stabilizer to exudation or volatilization during any processing step with polymer formulations during the preparation of sheet, film, fiber or other fabricated pellicles. The absence or essential absence of exuded or volatilized stabilizer on processing equipment (i.e., rollers, guides, orifices, and the like) increases significantly the times between required shut-downs of continuously operated process equipment and represents enormous practical and economic savings related to the specific stabilizer used.

                  TABLE A                                                          ______________________________________                                                    TGA Data                                                                       Isothermal  Scanning (at 10° C.)                                        at 280° C.                                                                          per minute                                                         Time (minutes)                                                                             Temperature °C. to                                          to Indicated Weight                                                                        Indicated Weight                                                   Loss of Stabilizer                                                                         Loss of Stabilizer                                      Stabilizer*  10%    50%    100%  10%    50%                                    ______________________________________                                         TINUVIN P    0.4    0.75   1.2   182    215                                    TINUVIN 350  0.6    1.0    1.8   210    247                                    CYASORB UV-5411                                                                             0.6    1.9    3.5   225    260                                    Compound 333 0.8    3.0    6.0   250    290                                    Compound 1   6.0    24.0   56.0  300    340                                    Compound 2   6.0    29.0   65.0  305    350                                    Compound 3   1.7    6.3    12.5  273    313                                    Compound S1  0.8    2.6    4.5   240    282                                    Compound S2  1.0    4.0    7.0   257    298                                    Compound S3  1.0    3.4    6.6   258    298                                    Compound S4  0.8    2.8    5.7   263    298                                    ______________________________________                                          *TINUVIN P is 2(2-hydroxy-5-methylphenyl)-2H-benzotriazole.                    TINUVIN 350 is                                                                 2(2-hydroxy-3-tert-butyl-5-sec-butylphenyl)-2H-benzotriazole.                  CYASORB UV5411 is 2(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole.            Compound 333 is                                                                2[2hydroxy-3-(1-phenylethyl)-5-methylphenyl2H-benzotriazole.                   Compound S1 is                                                                 2[2hydroxy-3-methyl-5-(α,dimethylbenzyl)phenyl2H-benzotriazole.          Compound S2 is                                                                 2[2hydroxy-3-(α,dimethylbenzyl)-5-methylphenyl2H-benzotriazole.          Compound S3 is                                                                 2[2hydroxy-3-(α,dimethylbenzyl)-5-tert-butyl-phenyl2H-benzotriazole      Compound S4 is                                                                 5chloro-2-[2hydroxy-3-methyl-5-(α,dimethylbenzyl)phenyl2H-benzotria     ole.                                                                      

Compound 1 (Examples 3 and 5) clearly exhibits much greater resistance to sublimation and exudation (much less volatility) than the prior art benzotriazole stabilizers. Compound 1 incorporated in a stabilized polymer composition would remain there during processing permitting excellent processability coupled with a final polymer pellicle with greater protection against subsequent light-induced deterioration.

EXAMPLE 12 Retention of Benzotriazole Stabilizers in Polycarbonate During Sheet Production

Polycarbonate (Lexan, General Electric) resin was formulated with 0.3% by weight of a number of 2-aryl-2H-benzotriazole light absorber stabilizers. The formulated resin was extruded at 600° F. (316° C.) into thin sheets. The resultant sheets were dissolved in methylene chloride and the polycarbonate precipitated with methanol. The amount of benzotriazole stabilizer retained in the polycarbonate sheet after fabrication was determined by gas chromatographic analysis.

The results are given on Table B.

                  TABLE B                                                          ______________________________________                                                        % Retained in Polycarbonate                                     Stabilizer*    Sheet after Fabrication                                         ______________________________________                                         TINUVIN 350     82                                                             CYASORB UV-5411                                                                                87                                                             Compound 333   100                                                             Compound 1     100                                                             ______________________________________                                          *See Table A for chemical names of these stabilizers.                    

These data confirm the results on Table A that the instant Compound 1 resists sublimation or exudation during processing. Compound 333 likewise exhibits good volatility resistance in this test.

EXAMPLE 13 Resistance to Loss During Cure and Weathering of Benzotriazole Stabilizers in Thermoset Acrylic Coatings

Several thermoset acrylic resin and an alkyd/acrylic resin systems were formulated with 2% by weight of several benzotriazole light absorber stabilizers and cast onto glass plates in 1μ thick coatings. The coatings were then cured by heating at elevated temperatures for selected periods of time. The loss of benzotriazole light stabilizer was then ascertained by UV-absorption analysis of the coatings. Any decrease in absorbance of the coatings can be correlated to loss of benzotriazole stabilizer during the curing step.

These cured coatings were also subjected to the accelerated (quick) weathering test (QUV) involving alternating 4-hour period of UV irradiation at 60° C. with a 4-hour period of condensation (rain) at 50° C. for each cycle for a total of 670 hours. Again any decrease in absorbance of the weathered coatings can be correlated to loss of the benzotriazole stabilizer during the curing and weathering period.

Results are given on Table C.

                                      TABLE C                                      __________________________________________________________________________     Absorbance Loss During Cure or Weathering (Percent)                                     Thermoset Acrylic Resin Systems                                                Single layer                                                                               2-Coat System                                                                              High Solids                                                                          Alkyd/Acrylic Resin                              Heated      Heated      Heated                                                                               Heated                                           25 min                                                                               After 20 min                                                                               After 30 minutes                                                                           30 minutes                                                                           After                             Stabilizer*                                                                             at 120° C.                                                                    Weathering                                                                           at 135° C.                                                                    Weathering                                                                           at 150° C.                                                                    at 125° C.                                                                    Weathering                        __________________________________________________________________________     TINUVIN 328                                                                             25    35    59    69    95    77    100                               Compound 333                                                                            2     17    8     26    37    12    96                                Compound 1                                                                              0      5    0     10     0     0    73                                __________________________________________________________________________      *TINUVIN 328 is 2(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole.          Compound 333 is                                                                2[2hydroxy-3-(1-phenylethyl)-5-methylphenyl2H-benzotriazole.             

As is seen from Table C, the instant compound exhibits far greater resistance to loss from the thermoset acrylic resin and alkyd/acrylic resin systems than do other benzotriazoles of the prior art. Compound 1 is discernibly less volatile than is Compound 333 of closely related structure.

EXAMPLE 14 Gloss Values of Acrylic Enamels and Lacquers Containing Benzotriazole Stabilizers after Weathering

Several thermoset acrylic enamels and a thermoplastic acrylic lacquer were formulated to include a benzotriazole light absorber stabilizer. Gloss values were compared for the initial enamel or lacquer and after exposure to an accelerated weathering test (QUV where each cycle includes 4 hours of UV at 60° C. and 4 hours of condensation at 50° C.).

Results are given on Table D.

                                      TABLE D                                      __________________________________________________________________________     20° Gloss Values of Enamels or Lacquers Containing                      Benzotriazole Stabilizers Before and After Weathering                                     Thermoset Thermoset                                                                               Thermoplastic                                               Acrylic Enamel A                                                                         Acrylic Enamel B                                                                        Acrylic Lacquer                                                  800 hours                                                                               800 hours                                                                               200 hours                                    Stabilizer*                                                                               Initial                                                                             QUV  Initial                                                                            QUV  Initial                                                                            QUV                                          __________________________________________________________________________     No stabilizers                                                                            65   15.4 67.3                                                                               25.1 77.8                                                                               23.1                                         1% TINUVIN 328                                                                            68.1 15.0 64.6                                                                               26.7 --  --                                           1% Compound 333                                                                           68.7 19.8 65.2                                                                               25.6 78.0                                                                               24.0                                         1% Compound 1                                                                             66.9 27.8 68.8                                                                               33.2 78.5                                                                               41.1                                         2% TINUVIN 328                                                                            64.8 16.6 59.2                                                                               23.1 77.1                                                                               33.5                                         2% Compound 333                                                                           68.6 19.4 63.5                                                                               30.3 77.4                                                                               41.0                                         2% Compound 1                                                                             66.7 27.2 69.3                                                                               39.0 79.1                                                                               41.0                                         __________________________________________________________________________      *See Table C for chemical name of these stabilizers.                     

Formulations containing Compound 1 consistently gave better gloss values after QUV weathering than did those containing prior art benzotriazoles.

EXAMPLE 15 Stabilization of Polyethylene Terephthalate

0.5% of the compound of Example 3 is added as a stabilizer to molten polyethylene terephthalate at 270° C. with stirring under a nitrogen atmosphere. The resulting formulated polymer is ground with solid carbon dioxide.

The stabilized composition is extruded at elevated temperature into a film with little loss of stabilizer. The film is then exposed to actinic radiation. The stabilized film retains desirable physical properties for a longer period than does a film prepared from unstabilized polyester.

EXAMPLE 16 Stabilization of Polycarbonate

Polycarbonate (Lexan, General Electric) is mixed in a compounding extruder with 0.3% of the compound of Example 5. The stabilized composition is extruded into a sheet at elevated temperature with little loss of stabilizer. The sheet maintains physical properties after exposure to UV light for a longer period than does a sheet containing no stabilizer.

EXAMPLE 17 2-Nitro-2'-hydroxy-3'-α,α-dimethylbenzyl-5-tert-octylazobenzene

The above-named product was obtained using the general procedure of Example 4a by coupling o-nitrobenzenediazonium chloride with 2-α,α-dimethylbenzyl-4-tert-octyl-phenol as a red crystalline solid, melting at 133°-134° C.

EXAMPLE 18 2-(2-Hydroxy-3-α,α-dimethylbenzyl 5-tert-octylphenyl)-2H-benzotriazole

When in following the general procedure of Example 3, an equivalent amount of 2-nitro-2'-hydroxy-3'-α,α-dimethylbenzyl-5'-tert-octylazobenzene was substituted for the o-nitroazobenzene intermediate of Example 2, the above-named product was obtained in the form of slightly off-white crystals melting at 88°-90° C. (Compound 3)

Analysis: Calc'd for C₂₉ H₃₅ N₃ O: C: 78.87; H, 7.99; N, 9.51. Found C: 79.21; H, 8.01, N, 9.55.

EXAMPLE 19 2-(2-Hydroxy-3-tert-octyl-5-α,α-dimethylbenzylphenyl)-2H-benzotriazole

When using the procedure of Example 3, an equivalent amount of 2-nitro-2'-hydroxy-3'-tert-octyl-5-α,α-dimethylbenzylazobenzene is substituted for the o-nitroazobenzene intermediate of Example 2, the above-named product is obtained.

The delamination of U.V. transparent automotive topcoats when applied over epoxy ester primer surfaces is a serious problem for automobile manufacturers. This problem is particularly exacerbated when the final coating film thickness is below specification. The incorporation of UV absorbers into the topcoats is indicated as a way to protect said topcoats from delamination and to prevent undue loss of gloss.

EXAMPLE 20 Gloss and Delamination Values of Topcoats of Thermoplastic Acrylic Lacquer

A silver metallic thermoplastic acrylic lacquer was formulated to include a benzotriazole light stabilizer and then was sprayed as a topcoat over a primer surface consisting of an epoxy ester on a metallic panel. The cure schedule was heating for 10 minutes at 48° C. and then for 30 minutes at 155° C. The initial topcoat film thickness was 2.0 to 2.2 mils (50 to 55 microns, 0.0508 to 0.0559 mm).

The panels were then exposed for one year in South Florida in an unheated black box at an angle of 5° to the sun.

The panels following the South Florida Black Box Exposure were conditioned for 96 hours in a constant humidity chamber at 38° C. and 100% relative humidity. The panels were then removed from the chamber, wiped dry and immediately evaluated using the cross-hatch tape adhesion test. The panels were then allowed to recover for one hour at room temperature before the cross-hatch tape adhesion test was run at a different spot on the same panel. Samples generally show some improved delamination resistance following the one hour recovery period from the most severe delamination condition namely immediately after humidification.

The cross-hatch tape adhesion test involves using a multi-cut knife to prepare cross-hatches through the topcoat film on the panel. A acetate fiber adhesive tape is placed over the cross-hatch area and then is pulled off. A visual inspection of the amount of topcoat, if any, coming off with the tape as it is pulled gives a relative rating of the amount of delamination. A rating system of 0 meaning no cross-hatch delamination to 5 meaning complete cross-hatch delamination is used.

Results are given on Tables E and F.

                                      TABLE E                                      __________________________________________________________________________     20° Gloss Values of Silver Metallic                                     Thermoplastic Acrylic Lacquer*                                                 After 5° South Florida Black Box Exposure                               Stabilizers    After 6  After 1 After 1                                        (% by wt.)**                                                                              Initial                                                                            Months (Florida)                                                                        Year (Florida)                                                                         Year Polished***                               __________________________________________________________________________      None      77.8                                                                               15.1     1.6     4.4                                            1% Compound 333                                                                           78.0                                                                               33.5     3.7     6.6                                            1% Compound 1                                                                             78.5                                                                               44.0     13.4    29.5                                           2% TINUVIN 328                                                                            77.1                                                                               34.9     8.5     13.7                                           2% Compound 333                                                                           77.4                                                                               41.0     9.5     28.0                                           2% TINUVIN 350                                                                            77.5                                                                               37.5     6.0     24.3                                           2% Compound 1                                                                             79.1                                                                               53.4     15.8    28.9                                           2% Compound 2                                                                             79.4                                                                               50.0     17.7    38.4                                           __________________________________________________________________________      *Thermoplastic acrylic lacquer is based on a binder of 60% poly(methyl         methacrylate), 20% cellulose acetate butyrate and 20% plasticizer with         about 3 phr of metallic pigment.                                               **See Tables A and C for chemical names of these stabilizers.                  ***One half of each panel was polished with DuPont #7 auto polish.       

                  TABLE F                                                          ______________________________________                                         Delamination Values of Silver Metallic                                         Thermoplastic Acrylic Lacquer*                                                 After One Year 5° South Florida                                         Black Box Exposure                                                                       Delamination Rating (0 to 5)                                                                   After One Hour                                                   Immediately after                                                                            Recovery at Room                                     Stabilizer**                                                                               Humidity      Temperature After                                    (% by wt.)  Conditioning  Humidity Conditioning                                ______________________________________                                          None       5             5                                                    1% Compound 1                                                                              2             1                                                    2% TINUVIN 328                                                                             5             2                                                    2% TINUVIN 350                                                                             3             2                                                    2% Compound 333                                                                            5             4                                                    2% Compound 1                                                                              2             2                                                    2% Compound 2                                                                              4             3                                                    ______________________________________                                          *See description of lacquer on Table                                           **See Tables A and C for chemical names of these stabilizers.            

The data on Table E confirm that the instant compound 1 and compound of instant Example 10 exhibit excellent resistant to loss during prolonged exposure in the South Florida Black Box test compared to other benzotriazole light stabilizers.

The data on Table F show that the instant compounds, particularly compound 1, protect a thermoplastic acrylic topcoat from delamination after one year of South Florida Black Box Exposure under the most severe testing conditions immediately following humidification.

EXAMPLE 21 Delamination Values of Topcoats of Thermoset Acrylic Enamels

Two silver metallic thermoset acrylic enamels were formulated to include a benzotriazole light stabilizer and then sprayed as a topcoat over a primer surface consisting of an epoxy ester on a metal panel. The cure schedule was 17 minutes at 130° C. to give an initial topcoat film thickness of 1.7 mils (42 microns, 0.0432 mm). This panel was then exposed for 1200 hours in the QUV weathering test described in Example 13.

The panels following the QUV exposure were humidified, then tested for delamination resistance, then allowed to recover for one hour and then retested for delamination resistance as described in Example 20.

Results are given on Table G.

                                      TABLE G                                      __________________________________________________________________________     Delamination Values of Silver Metallic                                         Thermoset Acrylic Enamel After                                                 1200 Hours QUV Exposure                                                                  Delamination Rating (0 to 5)                                                   Enamel* A         Enamel* B                                                            After One Hour    After One                                                    Recovery at       Hour Recovery                                        Immediately                                                                            Room Tempera-                                                                            Immediately                                                                            at Room Temper-                                      After Humi-                                                                            ture after                                                                               After Humi-                                                                            ature after                                Stabilizer                                                                               dity Condi-                                                                            Humidity  dity Condi-                                                                            Humidity                                   (% by wt.)                                                                               tioning Conditioning                                                                             tioning Conditioning                               __________________________________________________________________________      None     3       1         5       3                                          1% Compound 1                                                                            0       0         0       0                                          2% Compound 1                                                                            0       0         0       0                                          __________________________________________________________________________      *Thermoset acrylic enamel is based on a binder of 70% of acrylic monomers      such as hydroxyethyl acrylate, styrene, acrylonitrile, butyl acrylate and      acrylic acid with 30% of a malamine resin. Enamel A is a lower 40-45%          solids solution while Enamel B is a nonaqueous dispersion (NAD) having         about 45-50% solids with about 3 phr of metallic pigment.                

The combination of hindered amine light stabilizers and the instant benzotriazole UV light absorbers provides a particularly beneficial solution to the combined goal of gloss retention and delamination resistance in metallic thermoset acrylic enamels and in metallic thermoplastic acrylic lacquers for automotive topcoats.

The hindered amine light stabilizers even at low concentrations (0.5% by weight) protect the thermoset acrylic enamels and thermoplastic acrylic lacquers against loss of gloss, but do not act as UV light screens. Accordingly, UV light can pass through the acrylic topcoat in the absence of a UV light absorber, such as the instant benzotriazoles, and cause deterioration and failure in epoxy ester primer surface beneath the topcoat. Incorporation of even low concentrations (0.5% by weight) of a benzotriazole in combination with a hindered amine provides both gloss retention and resistance to delamination for the metallic acrylic topcoats.

EXAMPLE 22 Delamination Values of Topcoats of Thermoset Acrylic Enamels

Two silver metallic thermoset acrylic enamels were formulated to include both a hindered amine light stabilizer and a benzotriazole light absorber. Test panels were prepared and tested as described in Example 21.

Results are given on Table H.

                                      TABLE H                                      __________________________________________________________________________     Delamination Values of Silver Metallic                                         Thermoset Acrylic Enamel* After                                                1200 Hours QUV Exposure                                                                   Delamination Rating (0 to 5)                                                   Enamel A          Enamel B                                                             After One Hour    After One Hour                                               Recovery at       Recovery at                                          Immediately                                                                            Room Tempera-                                                                            Immediately                                                                            Room Tempera-                                        After Humi-                                                                            ture After                                                                               After Humi-                                                                            ture After                                Stabilizer**                                                                              dity Condi-                                                                            Humidity  dity Condi-                                                                            Humidity                                  (% by wt.) tioning Conditioning                                                                             tioning Conditioning                              __________________________________________________________________________      None      3       1         5       3                                         0.5% Compound A                                                                           1       0         5       2                                         1% Compound A                                                                             3       0         5       1                                         2% Compound A                                                                             3       0         5       1                                         0.5% Compound B                                                                           5       2         5       3                                         1% Compound B                                                                             4       2         5       0                                         2% Compound B                                                                             2       2         5       0                                         1% TINUVIN 328                                                                            0       0         0       0                                         2% TINUVIN 328                                                                            0       0         0       0                                         1% Compound 1                                                                             0       0         0       0                                         2% Compound 1                                                                             0       0         0       0                                         1% Compound A +                                                                           0       0         0       0                                         1% TINUVIN 328                                                                 1% Compound B +                                                                           0       1         0       0                                         1% TINUVIN 328                                                                 1% Compound A +                                                                           0       0         0       0                                         1% Compound 333                                                                1% Compound B +                                                                           1       0         0       0                                         1% Compound 333                                                                1% Compound A +                                                                           0       0         0       0                                         1% Compound 1                                                                  1% Compound B +                                                                           0       0         0       0                                         1% Compound 1                                                                  __________________________________________________________________________      *See description of thermoset acrylic enamel in Table G                        **See Table C for chemical names of Tinuuin 328 and Compound 333               Compound A is bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.                   Compound B is bis(1,2,2,6,6-pentamethyl-4-piperidyl)                           2n-butyl-2-(3,5,-di-tert-butyl-4-hydroxybenzyl)malonate.                 

EXAMPLE 23 Delamination and 20° Gloss Values of Thermoplastic Acrylic Lacquers

The efficacy of combinations of hindered amine light stabilizers and the instant benzotriazole light absorbers in providing highly beneficial protection to automotive topcoats is well demonstrated with thermoplastic acrylic resins wherein both gloss retention after prolonged exposure in South Florida is provided by the hindered amine component while the instant benzotriazole light absorber protects the thermoplastic acrylic topcoat from delamination.

A silver metallic thermoplastic acrylic lacquer was formulated to include both a hindered amine light stabilizer and a benzotriazole light absorber. Test panels were prepared and tested as described in Example 20.

Results are given on Table J.

                                      TABLE J                                      __________________________________________________________________________     Delamination and 20° Gloss Values of                                    Silver Metallic Thermoplastic Acrylic                                          Lacquer* After 5° South Florida                                         Black Box Exposure                                                                                           Delamination Values                                                            (0 to 5) After 1 yr. Exp                                                              After One                                             20° Gloss Values  Hour Re-                                                  After    After 1                                                                             Immediately                                                                           covery at                                 Stabilizers**   6 mos.                                                                             After 1                                                                             yr. (Fla)                                                                           After Humid.                                                                          rt. after                                 (% by wt.)  Initial                                                                            (Fla)                                                                              yr. (Fla)                                                                           polished                                                                            conditioning                                                                          condition                                 __________________________________________________________________________      None       77.8                                                                               15.1                                                                               1.6  4.4  5      5                                         0.5% Compound A                                                                            77.5                                                                               48.0                                                                               15.1 35.6 5      3                                         1% Compound A                                                                              77.2                                                                               42.0                                                                               36.2 39.7 5      5                                         2% Compound A                                                                              76.7                                                                               44.2                                                                               14.3 31.4 5      5                                         0.5% Compound B                                                                            77.9                                                                               45.0                                                                               38.5 45.6 5      5                                         1% Compound B                                                                              77.4                                                                               45.4                                                                               22.1 37.7 5      2                                         2% Compound B                                                                              76.8                                                                               45.3                                                                               26.5 46.0 5      3                                         2% TINUVIN 328                                                                             77.1                                                                               34.9                                                                               8.5  13.7 5      2                                         2% DOBP     77.5                                                                               35.0                                                                               6.8  19.7 3      2                                         1% Compound 333                                                                            78.0                                                                               33.5                                                                               3.7  6.6  --     --                                        2% Compound 333                                                                            77.4                                                                               41.0                                                                               9.5  28.0 5      4                                         1% Compound 1                                                                              78.5                                                                               44.0                                                                               13.4 29.5 2      1                                         2% Compound 1                                                                              79.1                                                                               53.4                                                                               15.8 28.9 2      2                                         1% Compound 2                                                                              79.4                                                                               50.0                                                                               17.7 38.4 4      3                                         2% TINUVIN 350                                                                             77.5                                                                               37.5                                                                               6.0  24.3 3      2                                         1% Compound A +                                                                            77.6                                                                               47.8                                                                               19.6 41.3 5      5                                         1% TINUVIN 328                                                                 0.5% Compound A +                                                                          78.3                                                                               50.2                                                                               21.4 39.4 5      4                                         0.5% Compound 333                                                              0.5% Compound B +                                                                          78.2                                                                               52.7                                                                               18.8 41.3 3      2                                         0.5% Compound 333                                                              1% Compound A +                                                                            78.4                                                                               49.6                                                                               21.7 39.0 5      4                                         1% Compound 333                                                                1% Compound B +                                                                            77.7                                                                               47.5                                                                               25.4 44.6 4      3                                         1% Compound 333                                                                0.5% Compound A +                                                                          78.2                                                                               47.1                                                                               16.0 37.2 3      2                                         0.5% Compound 1                                                                0.5% Compound B +                                                                          77.7                                                                               48.0                                                                               33.4 39.8 3      2                                         0.5% Compound 1                                                                __________________________________________________________________________      *See description of thermoplastic acrylic lacquer in Table E.                  **See Tables A, C and H for chemical names of stabilizers.                     DOBP is 4dodecyloxy-2-hydroxybenzophenone.                                

What is claimed is:
 1. An automotive topcoat finish, lacquer or enamel composition exhibiting retention of gloss and resistance to delamination on weathering which comprises(a) a thermoplastic acrylic resin or a thermoset acrylic resin, (b) 0.1 to 5% by weight of resin of a compound of the formula ##STR27## wherein T₁ is hydrogen or chloro, T₂ and T₃ are independently the group ##STR28## where T₄ is hydrogen or lower alkyl, T₅ is tert-octyl or the group ##STR29## T₆ has the same meaning as T₅, with the proviso that one of T₅ and T₆ must be tert-octyl, but both cannot be tert-octyl, and (c) 0.1 to 5% by weight of resin of a hindered amine light stabilizer.
 2. A composition according to claim 1 containing 0.5 to 2% by weight of component (b) based on resin, and 0.5 to 2% by weight of component (c) based on resin.
 3. A composition according to claim 1 wherein T₄ in component (b) is hydrogen.
 4. A composition according to claim 1 wherein component (b) is 2-[2-hydroxy-3,5-di(α,α-dimethylbenzyl)-phenyl]-2H-benzotriazole.
 5. A composition according to claim 1 wherein component (c) is a light stabilizer of the formula (II) ##STR30## in which n is a number from 1-4 inclusive; R is hydrogen or methyl; R₁ is hydrogen, oxyl, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₁ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl, C₃ -C₅ alkenoyl, glycidyl or a group --CH₂ --CH(OH)--Z wherein Z is hydrogen, methyl or phenyl; and R₂ when n is 1 is hydrogen, C₁ -C₁₈ alkyl optionally interrupted by one or more oxygen atoms, cyanoethyl, benzyl, glycidyl, a monovalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acid, or of carbamic acid or of a phosphorus-containing acid, or a monovalent silyl radical; R₂ when n is 2 is C₂ -C₁₂ alkylene, C₄ -C₁₂ alkenylene, xylylene, a bivalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid, of dicarbamic acid or of a phosphorus-containing acid, or a bivalent silyl radical; R₂ when n is 3 is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid, of an aromatic tricarbamic acid or of a phosphorus-containing acid, or a trivalent silyl radical; and R₂ when n is 4 is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid.
 6. A composition according to claim 5 where in the light stabilizer of Formula IIn is the number 1 or 2; R is hydrogen or methyl; R₁ is hydrogen, C₁ -C₁₂ alkyl, allyl, benzyl, acetyl or acryloyl; and R₂ when n is 1 is a radical of an aliphatic carboxylic acid having 2-18 C atoms, of a cycloaliphatic carboxylic acid having 5-12 C atoms or of an aromatic carboxylic acid having 7-15 C atoms; and R₂ when n is 2 is a radical of an aliphatic dicarboxylic acid having 2-36 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8-14 C atoms, or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 C atoms.
 7. A composition according to claim 1 wherein compound (c) is a light stabiliser of the formula (III) ##STR31## in which n is the number 1 or 2; R is hydrogen or methyl; R₁ is hydrogen, oxyl, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl or C₃ -C₅ alkenoyl; R₃ is hydrogen, C₁ -C₁₂ alkyl, C₅ -C₇ cycloalkyl, C₇ -C₈ aralkyl, C₂ -C₁₈ alkanoyl, C₃ -C₅ alkenoyl or benzoyl; and R₄ when n is 1 is hydrogen, C₁ -C₁₈ alkyl, C₅ -C₇ cycloalkyl, C₂ -C₈ alkenyl which is unsubstituted or substituted by a cyano, carbonyl or carbamide group, or it is glycidyl, a group of the formula --CH₂ --CH(OH)--Z or of the formula --CONH--Z wherein Z is hydrogen, methyl or phenyl; or R₄ when n is 2 is C₂ -C.sub. 12 alkylene, C₆ -C₁₂ arylene, xylylene, a --CH₂ --CH(OH)--CH₂ -- group or a group --CH₂ --CH(OH)--CH₂ --O--X--O--CH₂ --CH(OH)--CH₂ -- wherein X is C₂ -C₁₀ alkylene, C₆ -C₁₅ arylene or C₆ -C₁₂ cycloalkylene; or, provided that R₃ is not alkanoyl, alkenoyl or benzoyl, R₄ can also be a bivalent radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can also be the group --CO--; or R₃ and R₄ together when n is 1 can be the cyclic radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid.
 8. A composition according to claim 1 wherein component (c) is a light stabiliser of the formula (IV) ##STR32## in which n is the number 1 or 2; R is hydrogen or methyl; R₁ is hydrogen, oxyl, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl or C₃ -C₅ alkenoyl; and R₅ when n is 1 is C₂ -C₈ alkylene or hydroxyalkylene or C₄ -C₂₂ acyloxyalkylene; and R₅ when n is 2 is the group (--CH₂)₂ C(CH₂ --)₂.
 9. A composition according to claim 1 wherein component (c) is a light stabiliser of the formula (V) ##STR33## in which n is the number 1 or 2; R is hydrogen or methyl; R₁ is hydrogen, oxyl, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl or C₃ -C₅ alkenoyl; R₆ is hydrogen, C₁ -C₁₂ alkyl, allyl, benzyl, glycidyl or C₂ -C₆ alkoxyalkyl; and R₇ when n is 1 is hydrogen, C₁ -C₁₂ alkyl, C₃ -C₅ alkenyl, C₇ -C₉ aralkyl, C₅ -C₇ cycloalkyl, C₂ -C₄ hydroxyalkyl, C₂ -C₆ alkoxyalkyl, C₆ -C₁₀ aryl, glycidyl, a group of the formula --(CH₂)_(m) --COO--Q or of the formula --(CH₂)_(m) --O--CO--Q wherein m is 1 or 2, and Q is C₁ -C₄ alkyl or phenyl; or R₇ when n is 2 is C₂ -C₁₂ alkylene or C₆ -C₁₂ arylene, a group --CH₂ --CH(OH)--CH₂ --O--X--O--CH₂ --CH(OH)--CH₂ -- wherein X is C₂ -C₁₀ alkylene, C₆ -C₁₅ arylene or C₆ -C₁₂ cycloalkylene, or a group --CH₂ CH(OZ')CH₂ --(OCH₂ --CH(OZ')CH₂)₂ -- wherein Z' is hydrogen, C₁ -C₁₈ alkyl, allyl, benzyl, C₂ -C₁₂ alkanoyl or benzoyl.
 10. A composition according to claim 1 wherein component (c) is a light stabilizer of the formula (VI) ##STR34## in which n is the number 1 or 2; and R₈ is a group of the formula ##STR35## in which R and R₁ are as defined under the formula (II), Y is --O-- or --NR₁₁ --, A is C₂ -C₆ alkylene; and m is the number 0 or 1; R₉ is the groups R₈, NR₁₁ R₁₂, --OR₁₃, --NHCH₂ OR₁₃ or --N(CH₂ OR₁₃)₂ ; R₁₀ when n is 1 is the groups R₈ or R₉ ; and R₁₀ when n is 2 is the group --Y--Q--Y-- wherein Q is C₂ -C₆ alkylene optionally interrupted by --N(R₁₄)--; R₁₁ is C₁ -C₁₂ alkyl, cyclohexyl, benzyl or C₁ -C₄ hydroxyalkyl, or a group of the formula ##STR36## R₁₂ is C₁ -C₁₂ alkyl, cyclohexyl, benzyl, C₁ -C₄ hydroxyalkyl; R₁₃ is hydrogen, C₁ -C₁₂ alkyl or phenyl; and R₁₄ is hydrogen or the group --CH₂ OR₁₃ ; or R₁₁ and R₁₂ together are C₄ -C₅ alkylene or oxaalkylene, or R₁₁ and R₁₂ are each a group of the formula ##STR37##
 11. A composition according to claim 1 wherein component (c) is a light stabiliser of the formula (VII) ##STR38## in which n is the number 1 or 2; R is hydrogen or methyl; and R₁₄ when n is 1 is C₄ 14 C₁₈ alkyl, C₇ -C₁₂ aralkyl, the group --CO--R₁₅, or C₁ -C₄ alkyl which is substituted by --CN, --COOR₁₆, --OH, --OCOR₁₇ or ##STR39## wherein R₁₅ is C₁ -C₁₂ alkyl, C₂ -C₄ alkenyl or phenyl, R₁₆ is C₁ -C₁₈ alkyl, R₁₇ is C₁ -C₁₈ alkyl, C₂ -C₁₀ alkenyl, cyclohexyl, benzyl or C₆ -C₁₀ aryl; or R₁₄ when n is 2 is C₄ 14 C₁₂ alkylene, 2-butenylene-1,4, xylylene, the group --(CH₂)₂ --OOC--R₁₈ --COO--(CH₂)₂ -- or the group --CH₂ --OOC--R₁₉ --COO--CH₂ -- wherein R₁₈ is C₂ -C₁₀ alkylene, phenylene or cyclohexylene, and R₁₉ is C₂ -C₁₀ alkylene, xylylene or cyclohexylene.
 12. A composition according to claim 1 wherein component (c) is a light stabiliser of the formula (VIII) ##STR40## in which Q is --N(R₃)-- or --O--; E is C₁ -C₃ alkylene, the group --CH₂ --CH(R₄)--O-- wherein R₄ is hydrogen, methyl or phenyl, the group --(CH₂)₃ --NH-- or a single bond; R is hydrogen or methyl; R₁ is hydrogen, C₁ -C₁₈ alkyl, C₃ -C₈ alkenyl, C₃ -C₈ alkynyl, C₇ -C₁₂ aralkyl, C₁ -C₈ alkanoyl, C₃ -C₅ alkenoyl or glycidyl; R₂ is hydrogen or C₁ -C₁₈ alkyl; R₃ is hydrogen, C₁ -C₁₈ alkyl, C₅ -C₇ cycloalkyl, C₇ -C₁₂ aralkyl, cyanoethyl, C₆ -C₁₀ aryl, the group --CH₂ --CH(R₄)--OH wherein R₄ has the meaning defined above, a group of the formula ##STR41## or a group of the formula ##STR42## wherein G can be C₂ -C₆ alkylene or C₆ -C₁₂ arylene; or R₃ is a group --E--CO--NH--CH₂ --OR₂.
 13. A composition according to claim 1 wherein component (c) is bis-(2,2,6,6-tetramethyl-4-piperidyl)sebacate.
 14. A composition according to claim 1 wherein component (c) is bis(1,2,2,6,6-pentamethyl-4-piperidyl)2-n-butyl-2-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate. 